DE4137619A1 - MICROCAPSULES WITH SOLID CORE - Google Patents

Description

The present invention relates to new microcapsules Solid core, obtainable by suspension polymerization from

• A) 30 to 100 wt .-% of one or more vinyl monomers (Monomers I),
• B) 0 to 70 wt .-% of one or more bi- or polyfunk tional monomers (Monomers II) and
• C) 0 to 40% by weight of other monomers (monomers III),

the solid particles, the monomers and one or several oil-soluble radical initiators dispersed in water the and the polymerization in the usual way by the ther mix disintegration of the radical starter triggered and controlled becomes.

In addition, the invention relates to a method for manufacturing provision of these microcapsules and their use in the manufacture production of printing and painting inks and varnishes, for manufacture provision of toners for electrophotography, for dyeing of plastics and synthetic fibers and for the production of heat-sensitive recording materials.

Microencapsulated solids are known per se. Here han especially metals, metal oxides, pigments, Color formers and other inorganic or organic parts Chen who tend to agglomerate or their surfaces properties for the respective purpose should be lighted. You will be in many areas of the Technology used, for example in the production of Printing inks and varnishes, from heat sensitive records materials and toners for electrophotography.

In US-A-44 21 660, 46 80 200 and 47 71 086 are micro encapsulated solids where the encapsulation by polymerization of hydrophobic monomers, esp  special vinyl monomers, with water-soluble radical initiators takes place in aqueous dispersions. With this emulsion poly merisation, however, it is disadvantageous that an unavoidable one more or less large proportion of polymer particles that do not envelop solid particles.

From the older German patent application P 40 15 753.9 a process for the production of microcapsules in core contain dissolved color formers known. The Polymerisa tion is here using oil-soluble radical starter carried out in an oil-in-water emulsion. The Vinyl monomers used dissolve in the hydrophobic core solvent, while the resulting polymer is insoluble and after phase separation, the stable capsule wall around the liquid core forms.

The invention was based, microencapsulated the task Provide solid particles that are characterized by good distinguish technical properties and their Manufacturing does not have the disadvantages mentioned above.

Accordingly, the microcapsules defined at the outset were used Solid core found.

Furthermore, the method defined hereby became provision of these microcapsules and their use in the manufacture production of printing and painting inks and varnishes, for manufacture provision of toners for electrophotography, for dyeing of plastics and synthetic fibers and for the production of heat-sensitive recording materials found.

Micro enveloping the solid particles according to the invention capsules are made from 30 to 100 wt .-%, preferably 40 to 100% by weight of one or more vinyl monomers (monomers I) produced.

In addition, the microcapsules according to the invention can be made of bis 70% by weight, preferably up to 40% by weight, of one or more bi- or polyfunctional monomers (Monomers II) and from up to 40 wt .-%, preferably up to 30 wt .-% other Monomers (Monomers III) must also be built up.  

The monomers I and II are hydrophobic and un saturated compounds, each individually or in Form of mixtures can be used.

Suitable vinyl monomers I are, for example:

• - Monovinyl aromatics such as styrene and its derivatives substituted by halogen or C ₁ -C ₁₀ alkyl, for example vinyl toluene, α- and β-methylstyrene, n- and tert-butylstyrene, chlorostyrene and vinylpyridine;
• - C ₁ -C ₂₄ alkyl esters of α-β-unsaturated C ₃ -C ₁₀ carboxylic acids, especially of acrylic and methacrylic acid, such as especially methyl, ethyl, n-propyl, n-butyl and 2 -Ethylhexyl acrylate and methacrylate, also isopropyl, isobutyl, sec-butyl and tert-butyl acrylate and methacrylate, in addition n-pentyl, n-hexyl, n-heptyl, n-octyl and lauryl acrylate and methacrylate;
• - Vinyl esters of C ₂ -C ₂₀ carboxylic acids such as vinyl acetate and vinyl propionate;
• - vinyl halides such as vinyl chloride and vinylidene chloride;
• - C ₄ -C ₁₀ alkanedienes such as butadiene and isoprene.

Preferred monomers I are styrene, methyl, ethyl, n- Propyl, n-butyl and 2-ethylhexyl acrylate and / or meth acrylate.

The monomers II are bifunctional and polyfunctional monomers, primarily divinyl and polyvinyl monomers, which crosslinking of the capsule wall during the polymerization cause. Through the crosslinking, the polymer shell becomes Solids difficult to melt and thus get an essential one better temperature stability. At the same time, it is against the attack of solvents that the uncrosslinked Would solve polymers, stable.

Suitable divinyl monomers are, for example:

• - divinyl aromatics such as divinylbenzene;  
• - Diacrylates and dimethacrylates of C ₂ -C ₂₀ alkanediols such as, in particular, 1,3- and 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol diacrylate and dimethacrylate , also ethanediol and 1,3-butanediol diacrylate and dimethacrylate, in addition dipropylene glycol diacrylate, ethyl diglycol diacrylate and tripropylene glycol diacrylate;
• - α, β-unsaturated C ₃ -C ₁₀ alkyl esters of α, β-unsaturated C ₃ -C ₁₀ carboxylic acids and carboxylic acid derivatives such as allyl methacrylate and methallyl methacrylamide;
• - C ₄ -C ₁₀ alkane-1,3-dienes such as butadiene.

Preferred divinyl monomers are ethanediol diacrylate and di methacrylate, 1,3-butanediol dimethacrylate, methallyl methacrylate amide and allyl methacrylate. 1,3- and 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol diacrylate and dimethacrylate and divinylbenzene.

Preferred polyvinyl monomers are trimethylolpropane tri acrylate and trimethacrylate, pentaerythritol triallyl ether and triacrylate and pentaerythritol tetraacrylate and tetrameth acrylate.

As additional monomers III there are hydrophilic unsaturated ones Connections into consideration. Suitable monomers III are in for example:

• - α, β-unsaturated C ₂ -C ₆ carboxylic acids and their derivatives such as salts, amides, nitriles and esters; e.g. B. acrylic acid, methacrylic acid, maleic acid, itaconic acid; Sodium acrylate; Acrylic and methacrylamide, 3-dimethylamino propyl acrylate and methacrylamide and acrylic amido-2-methylpropanesulfonic acid; Acrylic and methacrylic nitrile; 2-hydroxyethyl and 3-hydroxypropyl acrylate and methacrylate; 2-aminoethyl acrylate and methacrylate, 2-dimethylamino and 2-diethylaminoethyl acrylate and methacrylate and glycidyl acrylate and methacrylate, 2-sul foethyl and 3-sulfopropyl acrylate and methacrylate;
• - aromatic hydrophilic vinyl compounds such as N-vinyl pyrrolid-2-one and styrene sulfonic acid;  
• - Tetraalkyl / arylammonium compounds that are α, β-unsaturated contain groups such as vinylbenzyltrimethylammonium chloride.

Micro enveloping the solid particles according to the invention are encapsulated by suspension polymerization of the monomers ren I and, if desired, the monomers II and / or III in prepared aqueous medium in which the monomers disper are greeded. The radical initiators used here are oil soluble and start and control the polymerization on be known way through its thermal decay.

The usual oil-soluble per oxo and azo compounds, advantageously in amounts of 0.1 to 5% by weight, based on the weight of the monomers, can be used individually or as mixtures can be set.

Preferred radical initiators are tert-pentyl peroxypivalate, Dilauryl peroxide, tert-pentyl-2-ethylhexanoate, dibenzoyl per oxide, tert-butyl peroxy-2-ethylhexanoate, di-tert-butyl per oxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, cumene hydroperoxide, 2,2'-azobis (4-methoxy-2,4-dimethylvalero nitrile); 2,2'-azobis (2,4-dimethylvaleronitrile) and 2,2'-azo bis (2-methylbutyronitrile).

Particularly preferred are tert-butyl peroxyneodecanoate, Di (3,5,5-trimethylhexanoyl) peroxide, tert-butyl peroxypiva lat, 4,4'-azobisisobutyronitrile and dimethyl-2,2'-azobisiso butyrate. These range in temperature from 30 to 100 ° C a half-life of 10 hours.

It can be advantageous in the polymerization according to the invention be the molecular weight of the resulting polymers apply. This can be done in a known manner by adding chains carrying reagents happen during the polymerization. Suitable substances for this are, for example, aliphatic Alcohols such as methanol, isopropanol and 1-buten-2-ol, tetra chlorocarbon and mercaptans such as tert-dodecyl mercaptan and thioglycolic acid esters such as ethyl and 2-ethylhexylthiogly kolat.  

For the microencapsulation according to the invention, prinzi all solids, both inorganic and organic cal, used under the reaction conditions are not or only slightly soluble in water and with the other reaction partners do not react. Of course Lich should be the size of the solid particles in one for Microcapsules are the usual range, d. H. around 10 nm up to 100 µm. The preferred particle sizes depend on each intended use. Generally, however, after the process according to the invention also ver larger particles be encapsulated.

Suitable inorganic solids are, for example Metals such as aluminum, lead, iron, cobalt, nickel, chromium, Copper, silver, gold, palladium, platinum, rhodium and zinc and their alloys and preferably metal oxides, such as in addition Silicon dioxide and magnesium oxide, especially magnetic oxides (for example magnetite, nickel and cobalt oxide) and as a pig effective oxides should be mentioned.

Before the microencapsulation according to the invention colorants are added, d. H. inorganic and organic pig elements, dyes, only a certain percentage (about up to 10 wt .-%) are soluble in water, and color formers (these are compounds that are themselves colorless or hardly are colored and their color in contact with an electron acceptor by donating an electron or picking up one Develop protons). For example, the usual ones for the production of printing inks and varnishes, for the Electrophotography, for textile dyeing and textile pigments used in pressure and in heat and pressure sensitive recording materials used color formers suitable.

The following may be mentioned in detail, for example:

• - inorganic pigments such as:
  Titanium dioxide, zinc white, zinc sulfide, lithopone and lead white;
  Iron oxide black, iron-manganese black, spinel black and carbon black;
  Chromium, chromium oxide and chromium oxide hydrate green and ultra marine green;
  Cobalt blue, ultramarine blue, iron blue and manganese blue; Ultramarine violet, cobalt violet and manganese violet; Iron oxide red, cadmium sulfoselenide, molybdate red and ultramarine red;
  Iron oxide brown, mixed brown, spinel and corundum phases and chrome orange;
  Iron oxide yellow, nickel titanium yellow, chrome titanium yellow, cadmium sulfide, chrome yellow, zinc yellow, alkaline earth metal chromates and Naples yellow;
  Cadmium zinc sulfide;
• - organic pigments such as:
  Azo pigments
  Monoazo pigments such as CI Pigment Yellow 1, 3, 98, 74 and 10;
  Disazo pigments such as CI Pigment Yellow 12, 13, 14, 17, 16, 113, 81 and 83 and CI Pigment Orange 13, 17 and 34,
  β-naphthol pigments such as CI Pigment Red 1 and 3 and CI Pigment Orange 5;
  lacquered azo pigments such as CI Pigment Red 49, 23, 53, 24 and 68, CI Pigment Red 57: 1, 48 and 52, CI Pigment Yellow 61 and CI Pigment Red 151;
  Naphthol AS pigments such as CI Pigment Red 112, 8, 17, 26, 22, 27, 12, 7, 28, 9 and 29, CI Pigment Orange 38 and 30 and CI Pigment Red 146, 31, 170, 32 and 187;
  Benzimidazolone pigments such as CI Pigment Yellow 120, CI Pigment Orange 36, CI Pigment Red 175 and 176, CI Pigment Violet 32 and CI Pigment Brown 25;
  Metal complex pigments
  Azo metal complex pigments such as CI Pigment Green 10;
  Isoindoline pigments such as CI Pigment Yellow 109, 110 and 185 and CI Pigment Red 180;
  Phthalocyanine pigments such as especially copper phthalocyanines such as preferably CI Pigment Blue 15;
  Quinacrodon pigments such as CI Pigment Violet 19 and CI Pigment Red 122 and 209;
  Perinone pigments such as CI Pigment Orange 43 and 68 and CI Pigment Red 194 and 67;
  Perylene pigments such as CI Pigment Brown 26 and CI Pigment Red 179, 190, 123, 149, 178 and 189;
  Anthraquinone pigments such as CI Pigment Violet 5: 1, CI Pigment Yellow 123 and 108, CI Pigment Red 177 and CI Pigment Blue 60 and 64, CI Pigment Yellow 24 and 74, CI Pigment Orange 40 and CI Pigment Red 168;
  Thioindigo pigments such as CI Pigment Red 88, 181 and 198 and CI Pigment Violet 36 and 38;
  Dioxazine pigments such as CI Pigment Violet 23, 88, 89 and 91;
  Alkali blue pigments;
  Quinophthalone pigments;
  Fluorescent pigments such as CI Solvent Yellow 44, CI Pigment Yellow 101 and CI Basic Violet 10.
• - Color formers:
  Lactones such as crystal violet lactone;
  Phthalides such as 3,3-bis (p-dimethylaminophenyl) -6-dimethyl aminophthalide;
  Fluoranes such as 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-dibutylaminofluoran, 2-anilino-3-methyl-6-isopentylethylaminofluoran, 2-anilino-3-methyl-6-cyclohexylmethylaminofluoran, 2- (2'-chlorophenylamino) -6-diethylaminofluorane and 2- (2'-chlorophenylamino) -6-dibutylaminofluoran.

The weight of the microcapsules according to the invention is ratio of solid to the sum of the monomers I, II and III usually between about 10: 1 and 1: 10. The im The amount of monomer required depends on the ge desired application and of course especially the size the solid particles. At least that for a mono molecular coverage of the entire surface of the fine ver divided solid required amount of monomer used  which can be calculated using known formulas. in the in general, the polymer shells have thicknesses of up to approximately 10 μm on.

The solid must be used for the microencapsulation according to the invention be finely dispersed in water. The dispersion can be in in a way that is common, for example, for pigments, respectively. The pigment is expediently counter waited for water and one or more dispersing agents first predispersed in a dissolver. There with coloring pigments to achieve high color strengths average diameter of the pigment particles are less than 1 µm should usually be a common dispersion for example in an agitator ball mill or a pearl mill connected. In some cases, the Predispersion can be dispensed with.

The usual ones are suitable as dispersing agents wise used water-soluble non-ionic and ionic polymers (both of which are also known as protective colloids ) as well as non-ionic, cationic and anionic ten side.

The selection of suitable dispersing aids is detailed case and is encapsulated by the one to be encapsulated Solid determined. Decision criteria are e.g. B. light Dispersibility of the solid in water except for the ge Desired particle size, high solids content of the dispersion at low viscosity before and after microencapsulation and good storage stability of the dispersions after the microver encapsulation.

Preferred water-soluble nonionic dispersing aid Medium are, for example, polyvinyl alcohol, partially hydro lysed polyvinyl acetates, polyvinyl pyrrolidone and its co polymers such as vinyl pyrrolidone / vinyl acetate copolymers, poly acrylic and methacrylamide and copolymers, the respective Contain monomers, cellulose derivatives such as hydroxyethyl, Carboxymethyl and methyl cellulose, gelatin and rubber arabic and their mixtures.  

The nonionic polymers are usually in quantities from 0.1 to 2000% by weight, preferably 0.5 to 1000% by weight, based on the solid to be encapsulated.

Suitable as water-soluble ionic dispersing aids especially polyacrylic and methacrylic acid and copoly mers containing the respective monomers, copolymers the base of maleic acid and its anhydride, e.g. B. with Methyl vinyl ether, diisobutene and styrene, polymers from Sul foethyl and sulfopropyl acrylate and methacrylate, N-sulfo ethyl maleimide, 2-acrylamido-2-alkyl sulfonic acids, Styrene and vinyl sulfonic acid and copolymers of these monomers ren. Naphthalenesulfonic acid / are particularly preferred. Formaldehyde condensates, phenolsulfonic acid / formaldehyde con densate and polyacrylic and polymethacrylic acid.

The amount of ionic polymers used is in total 0.1 to 1000 wt .-%, preferably 0.5 to 500% by weight, based on the solid to be encapsulated.

Furthermore, surfactants can also be used as additional dispersants tools are added. Suitable nonionic ten side are, for example, sorbitan esters such as sorbitan laurate, Alkyl or aryl polyglycol ethers such as dodecyl polyglycol ether (with 18 ethylene oxide units). As a cationic surfactants For example, alkylammonium and alkylpyridinium salts such as cetyl trimethyl ammonium bromide and lauryl pyridinium chloride called. Examples of suitable anionic surfactants are Alkyl and alkylaryl sulfates and sulfonates such as sodium lauryl sulfate and nonylphenyl sulfonate, alkyl polyglycol ether and alkylphenol polyglycol ether sulfates and sulfonates such as Sodium lauryl polyglycol ether sulfate and nonylphenol poly glycol ether sulfonate (each with 50 EO units), alkyl sulfosuccinates such as sodium dioctyl sulfosuccinate and alkali metal salts of fatty acids such as potassium dodecanoate.

The surfactants are usually in amounts from 0.1 to 100 wt .-%, preferably 0.5 to 50 wt .-%, based on the encapsulating solid added.  

Depending on the type and duration of the dispersion, the size ver division of the solid particles on the respective uses intended purpose. Usually have the part Chen sizes from about 10 nm to 100 microns.

In the method for microencapsulation according to the invention can be done as usual: The solid is with submitted to the dispersing agents dispersed in water. The subsequent addition of monomers can be done in one step follow, but the monomers can also during the polymeri sation are gradually metered in, which is particularly cheap is when you have a layered structure of the polymer shell wants to achieve. The radical starter or the radical starter mixed and, if desired, the controller can also add directly with the monomers or gradually. It is also possible the dispersion after adding monomers and starters to continue.

The dispersion is then stirred vigorously on the Temperature heated at which the radical starter is sufficient corresponding quantities disintegrate. At this temperature the Polymerization carried out. It can also be cheap that The temperature of the mixture is then also stirred to increase slightly for a few more hours.

As a rule, the polymerization is carried out at 20 to 100 ° C. preferably at 40 to 80 ° C.

The polymerization is expediently carried out at normal pressure made, but you can also with reduced or work slightly increased pressure, i.e. in the range of 0.5 up to 5 bar.

As is known from US-A-44 21 660 and 46 80 200, it is also possible before and during the polymerization ultrasound to act on the dispersion to better dis pergation of the solid in water or to obtain a more uniform deposition of the polymer on the cap to reach a blinding solid.

The response times are usually 1 to 10 mei at least 2 to 7 hours. The rate of polymerization can by the choice of temperature and the amount of  Radical starter and controller ge in a conventional manner be controlled.

You can microencapsulated manufactured according to the invention Solids depending on the application in the form of the accumulated use aqueous dispersions, or you can use them for Dry the game by spray or freeze drying and as Use powder or re in water before use disperse.

The microencapsulated solids according to the invention can can be used advantageously for many purposes. this applies especially for the encapsulated colorant particles.

Microencapsulated pigments according to the invention are suitable excellent for the production of printing inks (both for Pa pier as well as for textile printing), paints and varnishes. Their use for water-dilutable is particularly favorable Systems because the aqueous dispersions of these pigments are very stable and therefore storable and easy to use with water are diluted. The colors and varnishes to be preserved show high color strength and at the same time excellent hiding power gen and are characterized by the special host economics of their application.

Encapsulated pigments can also be used according to the invention partly used for the production of toners for electrophotography phie be used. Especially when generating Color copies namely affects the different elek trical chargeability of the different toner pigments in part. This interference can be caused by microencapsulation conditions can be significantly reduced since the surface properties and thus also the chargeability of the pigment part Chen be standardized. Because the pigments in the toner manufacturing usually at high temperatures (about 100 up to 200 ° C) must be incorporated into the so-called toner resins microencapsulation with heavy is recommended fusible polymers, d. H. the monomers I are preferred together with the crosslinking monomers II polymeri siert.  

Also when dyeing plastics and synthetic fibers, especially other polyamide fibers can be microencapsulated according to the invention Pigments are used effectively. The dyeing is done here by incorporating the pigments directly into the respective Polymer melts at high temperatures up to over 300 ° C fig using extruders. You can't do that partially dissolve encapsulated pigments or with the poly melt melt react, which leads to a loss of color strength. A temperature-stable microencapsulation can also pigments which are not stable under these conditions are effective be protected. Here too, the monomers I are preferred polymerized together with the crosslinking monomers II.

An advantageous application of the microencapsule according to the invention ter color former consists in the production of heat sensitivity recording materials. It is in usually around paper or plastic films that are caused by on paint the aqueous dispersion of color formers and Color developers (electron acceptors such as phenols in particular derivatives and organic acids and their salts) coated have been. Through selective heat exposure with a Thermal printer is the coloring reaction between the triggered both components. An unwanted advance winding, d. H. a quality reducing background coat exercise can already be done during the production of the thermal paper can be prevented by microencapsulation of the color former. To enable the required coloring reaction, the capsule walls must be easily meltable, d. H. they be preferably consist of polymers of monomers I.

Examples A) Production of microcapsules with a solid core

The in the following examples for the water-soluble Po Polymeric K values were in each case H. Fikentscher, Cellulosechemie, Volume 13, pp. 48-64 and 71-74 (1932) in 1% by weight aqueous solution (or at K values less than 30 in 5% by weight aqueous solution) at 25 ° C Right.  

example 1

55 g C.I. Pigment Yellow 185 (isoindoline yellow, Paliotol® D 1155, BASF) and 6 g of the 30% by weight aqueous solution Phenolsulfonic acid condensate (Tamol®DN, BASF) were in 53 g of water at room temperature with a dissolver 4000 rpm dispersed in a beaker for 2 min. After encore a solution of 4 g of polyvinylpyrrolidone (K value 90) in 69 g Water was dispersed for a further 25 minutes. After further train be of 13 g of methyl methacrylate, 5.6 g of 1,4-butanediol diacrylate, 0.14 g of azobisisobutyronitrile and 0.2 g of dimethyl-2,2'-azobis Isobutyrate was dispersed for a further 30 min.

Then the dispersion was in a glass flask with a propeller stirrer (400 rpm) heated to 60 ° C and 2 h at this temperature held. This was followed by a further 4 h at 65 ° C polymerized.

Microencapsulated pigment with a particle was obtained size from <1 to about 100 µm.

Example 2

60.5 g C.I. Pigment Red 81: 1 (C.I. 45160: 3, Fanal® Rosa D 4830, BASF) and 64 g polyvinylpyrrolidone (K value 30) in 150 g of water in a Dispermat (tooth lock washer 3.5 cm Diameter, 5000 rpm) dispersed for 1 h. Then was the tooth lock washer against a Teflon washer (9 cm diameter) exchanged, glass balls (3 mm diameter) were added and then dispersion was continued at 3000 rpm for 1 h. To Zuga be of 6 g of Tamol DN was analogous to Example 1 with the ge there called monomers polymerized.

Microencapsulated pigment with a particle was obtained size from <1 to about 3 µm.

Example 3

55 g C.I. Pigment Red 81: 1 (as in Example 2) and 64 g of one unneutralized polyacrylic acid (K value 20) were in 240 g water in a Dispermat (Teflon disc 9 cm through  knife, 300 g glass balls 3 mm diameter, 3500 rpm) 3 h dispersed.

After adding 13.1 g of methyl methacrylate, 5.6 g of 1,4-butane diol diacrylate, 0.17 g tert-butyl peroxypivalate and 208 g Water was the dispersion in a glass flask with Propel Stirrer (400 rpm) heated to 59 ° C and 2 h at this tem temperature kept. This was followed by a further 4 h at 62 ° C polymerized.

Microencapsulated pigment with a particle was obtained size from <1 to about 5 µm.

In the examples listed in Table 1, Dis Pergulation and microencapsulation of 55 g C.I. pigment Red 81: 1 analogous to example 3.  

Table 1

Examples 7 to 12

In Examples 7 to 12 listed in Table 2 followed by the dispersion of 27.5 g of C.I. Pigment Yellow 185 (as example 1) analogous to example 2.

After further addition of a dispersing agent, the microencapsulation was carried out analogously to Example 3.

Example 13

55 g C.I. Pigment Blue 15: 3 (C.I. 74160, Heliogen® Blue K 7090, BASF) and 66 g polyvinyl pyrrolidone (K value 30) were in 154 g of water in a Dispermat (Teflon disc 9 cm diameter, 275 g glass balls 3 mm diameter, 3500 rpm) dispersed for 3.5 h. Then first 6 g of Tamol DN and 150 g of water and then 13.1 g of methyl methacrylic lat, 5.6 g 1,4-butanediol diacrylate and 0.17 g tert-butyl peroxypivalat added.

The polymerization was carried out analogously to Example 3.

Microencapsulated pigment with a particle was obtained size from <2 to about 6 µm.

Example 14

55 g C.I. Pigment Yellow 184 (spinel pigment, Sicopal® Yellow L1112, BASF) and 66 g vinyl pyrrolidone / vinyl Acetate 1.5: 1 copolymer (K value 25) were in 154 g Was water in a Dispermat (telephone disc 9 cm in diameter, 3500 rpm) dispersed for 3 h. Then initially 6 g of Tamol DN and then 13.1 g of methyl methacrylate, 5.6 g of 1,4-butane diol diacrylate and 0.17 g of tert-butyl peroxypivalate added.

The polymerization was carried out analogously to Example 3.

Microencapsulated pigment with a particle was obtained size from <1 to about 25 µm.

Examples 15 to 17

In Examples 15 to 17 listed in Table 3 followed by the dispersion of 55 g of the specified Pigments in the same amount of water analog Example 14 with 66 g vinyl pyrrolidone / vinyl acetate 1.5: 1 copo lymerisate (K value 25). The further treatment was just if analogous to Example 14 with the monomer / specified therein Starter mixture carried out.  

Table 3

Example 18

55 g of the diaminofluorane Pergascript® Schwarz I-R (Ciba-Gei gy) and 66 g of polyvinylpyrrolidone (K value 30) were analogous Example 3 dispersed in 154 g of water. The further treatment Example 13.

Microencapsulated color formers were obtained with a Particle size from <1 to about 25 microns.

B) Checking the microencapsulation

1. Testing the color strength of spreads according to the invention microencapsulated pigments.

Of the microencapsulated pigments listed in Table 4 aqueous dispersions of the were also applied there listed pigment levels using an 18 µm roller doctor blade coated white base paper. These spreads were then air dried.

The papers thus obtained were measured with an Elrepho filter photometer (from Zeiss). According to DIN 5033, the reflectance lines R _X , R _Y and R _{Z were used to determine} the standard color values X, Y and Z, from which the position in the L *, a *, b * color space (CIE 1976) was calculated. The saturation C * = (a ^{* 2} + b ^{* 2} ) ^1/2 can be regarded as a measure of the color strength.

Dispersions of the unencapsulated were used for comparison Pigments doctored by dispersion in the presence of polyvinyl pyrrolidone (K value 30).

The results are summarized in Table 4.  

Table 4

2. Testing a microencapsulated color according to the invention educator.

The color former dispersion obtained in Example 18 (28.7% by weight) was coated with a 15 µm Nehmer paper (Köhler, Oberkirch), which already the Ent winder contains, applied. The paper changed color there at not.

Even after spraying with Do acting as a solvent Only a few black spots were observed in decylbenzene.

The comparison test with unencapsulated Pergascript Schwarz I-R already gave without spraying with dodecylbenzene an intense blackening of the slave paper.

Claims (9)

1. Microcapsules with a solid core, obtainable by suspension polymerization of

• A) 30 to 100% by weight of one or more vinyl monomers (monomers I),
• B) 0 to 70 wt .-% of one or more bi- or polyfunctional monomers (monomers II) and
• C) 0 to 40% by weight of other monomers (monomer III),

the solid particles, the monomers and one or several oil-soluble radical initiators dispersed in water and carry out the polymerization in the usual way triggered the thermal decay of the radical starter and is controlled. 2. Microcapsules with solid core according to claim 1, in wel the solid particles are solid colorant particles are. 3. A process for the preparation of microcapsules with a solid core according to claim 1, characterized in that solid particles, a mixture of

• A) 30 to 100% by weight of one or more vinyl monomers (monomers I),
• B) 0 to 70 wt .-% of one or more bi- or polyfunctional monomers (monomers II) and
• C) 0 to 40% by weight of other monomers (monomers III)

and one or more oil-soluble radical initiators in What water dispersed, then the polymerization to usual  Way the thermal decay of the radical starter triggers and controls and the cap selen from polymer shell and solid core ge if desired in a manner known per se from the separates aqueous phase and dries. 4. Use of the microcapsules with a solid core according to claim 1 or 2 for the production of pressure paints, paints and varnishes. 5. Use of the microcapsules with a solid core according to claim 1 or 2 for the production of toners for electrophotography. 6. Use of the microcapsules with solid core ge according to claim 1 or 2 for coloring plastics and synthetic fibers. 7. Use of the solid-core microcapsules according to claim 1 or 2 for the production of heat-sensitive recording materials.